In a virtual world, encounters between avatars enable interlocutors represented by these avatars to exchange information with one another. When a virtual world is successful, a set of problems and issues arise, related to the numbers of participants generated by the attraction that users have to this virtual world.
From a technical viewpoint the resources needed for managing all the avatars of a virtual world cannot be indefinitely extended. Indeed, to implement a virtual world, a set of resources must be available. These are especially information technology resources (such as servers or network means) available to a service provider. The main task of such information technology servers is to pass on the changes undergone by each avatar to the other avatars present in the same virtual world that they share. When the number of avatars present in a virtual world increases, the server (or the group of servers) managing this world must manage such changes, most usually linearly, and sometimes exponentially in terms of load increases or more generally load variations.
From the viewpoint of a user connected to the virtual world, displaying all the avatars present may therefore raise problems of load management even when the number of these avatars increases appreciably especially for low-power terminals. Indeed, in the general mechanisms for managing virtual worlds, resources are often used within customer stations (i.e. stations of the users of the virtual world) to compute and display scenes (using specific languages such as the VRML (or Virtual Reality Modeling Language). Such computations consume power at the user terminals (involving the use of one or more microprocessors, virtual memory etc).
The existence of a large number of avatars also poses a direct problem to the user who then has difficulty in apprehending all the avatars present in his environment. For example, in the case of a virtual world designed to encourage meetings with other people in the virtual world who are using avatars, the presence of a thousand avatars risks being counter-productive (just as it would be difficult to set up a meeting in a crowd of a thousand individuals).
A commonly accepted limit today in the management of avatars within a virtual world is about 100 avatars simultaneously hosted on a “low-range” hardware server. This limit is soon reached in virtual worlds put online on the Internet, or even greatly exceeded with up to several thousands of simultaneous users for popular online sites.
There are techniques for circumventing these limits by building several virtual worlds which are then supported on one or more different server apparatuses. In the case of a server apparatus controlling several virtual worlds, it is possible to distinguish several entities in this server, called management or control entities, each dedicated to the management of one virtual world. It then becomes possible to identify a control entity on a server apparatus with a specific virtual world. In such an architecture, each terminal of a user of one of these specific worlds then needs to display only the avatars of the users that are connected to its world and enter their field of vision. Furthermore, each control entity on a server apparatus needs to have only the resources necessary for managing a subset of the users (i.e. the users of a specific world). However, the virtual worlds are in actual fact sealed off from each other.
One problem of this prior-art technique therefore lies in the way in which the changing of worlds is managed from the viewpoint of the users and from the viewpoint of the control entities on the servers. Indeed, this architecture obligatorily causes a compartmentalized separation between the worlds. To overcome this separation, service providers build several virtual worlds connected by passages, often called gates or portals, that are visible in varying degrees.
The problem then, at the technical level, is that of synchronizing the “gates” between the worlds and, at the economic level, that of the cost of achieving the visual aspect of each of these worlds. This approach however has the advantage of transparency for the customer but at high cost and lengthy implementation of the extensions of server apparatuses involving additional servers.
Other service providers economize on the cost of the visual aspect of the worlds by using the same visual aspect each time but with total separation between the different clone worlds. The user must thus choose the world to which he will be going prior to immersion. When he wishes to meet avatars from other worlds, he must change worlds. This approach has the advantage of low cost and fast implementation of extensions for server apparatuses but entails much inconvenience to the user, making his overall appreciation and experience of the service a negative one.
Indeed, the user is unable, within a same world, to meet all the avatars whom he might know and with whom he may have affinities. The user is therefore required to change worlds to meet other avatars. He must therefore manually disconnect from the current virtual world and then reconnect to another virtual world, which is not very practical and hampers the use of such services.
Furthermore, these different approaches in no way resolve the problem of the load of the control entities in the servers since the user can always choose to penetrate a virtual world as an extra load. It is furthermore this choice that he will most usually be making, identifying load with the success or efficiency of the virtual world.
Another drawback of these approaches is that imbalances may appear in these different virtual worlds, (for example between the number of women and the number of men in the case of a dating site) and if all the virtual worlds are identical in terms of construction, a user will not know in principle which virtual world will be most suited to his expectations.